As I mentioned before, I don't know what the reasons were for the plea deal, but prosecutors in the US, especially in the bigger cities, are definitely in the business of getting guaranteed convictions with plea deals, very often to the revolt of the victims.
US law is funny that way, because in this case, the worse charge, carrying the highest minimum sentence, was that of wilful property damage, which in my opinion is the least of the problems in this case.
FTR, I don't think what he allegedly did, deserved 5-25 years jail, but it definitely deserved more than community service imo.
In fact the civil suit was brought on 2 months later as a result of the dissatisfaction from the victims with the plea deal offered to him, and it appears a jury of his peers agreed with them.